Thursday, December 22, 2016

Changed emulator board design and sent to fab


My early testing with the Emulator role PCB shows that it is not going to work properly. The signals going from the fpga to the Alto require pull-up and pull-down resistors to give the ribbon cable termination. This should have been placed on the Alto side, but they were not, instead terminating the signals that ran from Diablo to Alto by resistors on the drive side.

I need to expand the PCB to add a pair of resistors per outgoing signal, a total of 22 added resistors. Good thing I only ordered one board for $66, of course with shipping and tax on top, as it is wasted. Time to get to the designing (and to order more components).

I had the 1401 restoration team meeting yesterday and spent quite a bit of time chasing down a flaw that resulted in card reader error stops. Greatly improved now, so that programs which use the read then print instruction can get through hundreds of cards before stopping. It had been failing on the third card pretty regularly.

Thursday morning I changed the emulator card design to add in the termination resistors and decided to send out for a new card through the same fast turnaround service I used previously. Another $100 and should be about two weeks to receive it.

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